A transformer is connected to an AC mains supply of 230 V. The primary coil has 4600 turns. The output of the secondary coil is to be connected to two identical lamps. To operate at full brightness, each lamp requires a potential difference of 12 V. At a lower voltage, the lamps will still light up but will be dimmer.
State how the two lamps should be connected across the output of the transformer so that they both operate at full brightness. Explain your answer.
Calculate the number of turns needed in the secondary coil to provide an output voltage of 12 V.
The two lamps are now connected in series across the output of the transformer. Describe and explain the effect on the brightness of the lamps.
275 exam-style questions on CIE IGCSE Physics 4.5 Electromagnetic effects, covering 4.5.1a Electromagnetic induction, 4.5.1b Direction of an induced e.m.f., 4.5.2 The a.c. generator, 4.5.3a Magnetic effect of a current and its applications, 4.5.3b Strength and direction of the field around wires and solenoids, 4.5.4a Force on a current-carrying conductor, 4.5.4b Force on beams of charged particles, 4.5.5 The d.c. motor, 4.5.6a Construction and operation of a transformer, 4.5.6b Turns ratio and current in a transformer, and 4.5.6c High-voltage transmission of electricity. Each one has a worked solution and a mark scheme showing where the marks go.